Roll Dart SDK from 23cdf0997052 to f79253a6b189 (2 revisions) (flutter#25499)

Author: skia-flutter-autoroll

DEPS

@@ -35,7 +35,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/master/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '23cdf099705216b22e91ec0d18bc39f9e8e4a668',
+  'dart_revision': 'f79253a6b1899cbfc323347a142c7d4b2f3345e9',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py